*: merge some basic enhancements to 8.5 to support get commit ts (#65871)

[lcwangchao]

ref #64281, close #64537

What problem does this PR solve?

Issue Number: ref #64281

What changed and how does it work?

• model: add minimal info for active-active table #64512
• model: reserve active-active feature definitions #65295
• unistore: unistore supports to return commit timestamp #65282
• *: tidb txn supports to setting WithReturnCommitTS #65306

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No need to test

  • I checked and no code files have been changed.

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[codecov]

Codecov Report

❌ Patch coverage is 78.26087% with 60 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (release-8.5-20260121-v8.5.5@1fa258b). Learn more about missing BASE report.

Additional details and impacted files

@@                       Coverage Diff                        @@
##             release-8.5-20260121-v8.5.5     #65928   +/-   ##
================================================================
  Coverage                               ?   73.1493%           
================================================================
  Files                                  ?       1681           
  Lines                                  ?     469340           
  Branches                               ?          0           
================================================================
  Hits                                   ?     343319           
  Misses                                 ?     103172           
  Partials                               ?      22849           

Flag	Coverage Δ
integration	50.9268% <52.8985%> (?)
unit	64.8637% <78.2608%> (?)

Flags with carried forward coverage won't be shown. Click here to find out more.

Components	Coverage Δ
dumpling	52.9278% <0.0000%> (?)
parser	∅ <0.0000%> (?)
br	63.8239% <0.0000%> (?)

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[lcwangchao]

/retest

[lcwangchao]

/retest

[ti-chi-bot]

[LGTM Timeline notifier]

Timeline:

• 2026-01-30 09:38:01.337935912 +0000 UTC m=+1350708.951892758: ☑️ agreed by tiancaiamao.
• 2026-01-30 12:06:21.541880246 +0000 UTC m=+1359609.155837092: ☑️ agreed by time-and-fate.

[ti-chi-bot]

[APPROVALNOTIFIER] This PR is NOT APPROVED

This pull-request has been approved by: cfzjywxk, tiancaiamao, time-and-fate
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Details

Needs approval from an approver in each of these files:

• OWNERS [cfzjywxk,tiancaiamao,time-and-fate]
• pkg/ddl/OWNERS
• pkg/disttask/OWNERS
• pkg/lightning/OWNERS
• pkg/meta/OWNERS
• pkg/table/OWNERS [cfzjywxk]

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